The invention relates to a gel-forming mixture of alkali metal silicate, water, one or more trialkoxysilanes of the formula R-Si(OR').sub.3, in which R is an aliphatic moiety of 1 to 6 carbon atoms and R' represents equal or different alkyl moieties of 1 to 4 carbon atoms, as gelling agent, and an additional substance for adjusting the setting time and/or gel strength.
Examples of trialkoxysilanes suitable for use in the invention are n-propyltrimethoxysilane, isobutyltrimethoxysilane, n-propyltriethoxysilane, isobutyltriethoxysilane and vinyltrimethoxysilane.
Liquid mixtures which contain in appropriate amounts the alkali metal silicates, water and trialkoxysilanes of the formula R-Si(OR').sub.3 form gels of low permeability to water, and a strength that increases with the passage of time (cf. German Offenlegungsschrift No. 31 51 680). By the injection of the liquid mixtures into permeable, unstable soils, these soils can be sealed and stabilized. The setting time of the mixtures and the strength of the resultant gels can be affected by additive substances. These substances can be, for example, hydroxides and alkalinely reacting salts of the alkali metals or known agents for gelling alkali silicate solutions.
The gel-forming injection mixtures containing trialkoxysilanes are also used for preventing the penetration of pollutants into ground water.
It is the object of the present invention to obtain an improved composition for gel-forming mixtures of alkali metal silicate, water and a trialkoxysilane, with an additive to provide good control of setting times and gel properties.